White, Leonard D.
Macmillan, 1955
Buku Teks
Waldo, Dwright
Random House, 1965
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Scmidt-Bleek, F
Tenn. Center for Business and Economic Research University of Tennessee, 1972
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Univ. of Tennessee
The health and safety dept., 1973
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Simon, Herbert A.
Alfred A. Knopf, 1973
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